External material accession systems and methods

Abstract

Methods, apparatus and systems are provided for introducing large numbers of different materials into a microfluidic analytical device rapidly, efficiently and reproducibly. In particular, improved integrated pipettor chip configurations, e.g. sippers or electropipettors, are described which are capable of sampling extremely small amounts of material for which analysis is desired, transporting material into a microfluidic analytical channel network, and performing the desired analysis on the material.

What is claimed is:  
     
       1. A method of sampling a first fluid, comprising: 
       (a) dipping an open end of an open ended fluid-filled capillary element into a source of the first fluid;  
       (b) withdrawing the capillary element from the first fluid;  
       (c) permitting an amount of the first fluid remaining on the open ended capillary to spontaneously inject into the capillary channel, thereby injecting the first fluid into the capillary channel;  
       (d) dipping the capillary element into a second fluid after a first selected time period, the first selected time period being controlled to control the amount of the first fluid permitted to spontaneously inject into the open ended capillary channel.  
     
     
       2. The method of  claim 1 , further comprising: 
       dipping the open end of the capillary element into a source of a third fluid after dipping the capillary into the source of second fluid;  
       withdrawing the capillary from the third fluid;  
       permitting an amount of the third fluid remaining on the open ended capillary to spontaneously inject into the capillary channel;  
       dipping the capillary into the second fluid after a second selected time period, the second selected time period being controlled to control the amount of the third fluid permitted to spontaneously inject into the open ended capillary channel.  
     
     
       3. The method of  claim 1 , further comprising transporting the amount of first fluid through the capillary for a second selected time, the second selected time being selected to control an amount of dilution of the amount of first fluid. 
     
     
       4. The method of  claim 3 , wherein the second selected time is controlled by controlling a flow rate of the amount of the first fluid through the capillary. 
     
     
       5. The method of  claim 3 , wherein the second selected time is controlled by selecting at least one of a length or a diameter of the capillary channel. 
     
     
       6. The method of  claim 1 , further comprising applying an electric field along a length of the capillary channel to electrokinetically transport the first fluid through the capillary channel. 
     
     
       7. The method of  claim 1 , further comprising applying pressure along the length of the capillary channel to transport the first fluid through the capillary channel. 
     
     
       8. The method of  claim 1 , further comprising introducing an amount of a low salt buffer into the capillary channel before injecting the amount of first fluid into the capillary channel. 
     
     
       9. The method of  claim 1 , further comprising introducing an amount of low salt buffer fluid into the capillary channel after injecting the amount of first fluid into the capillary channel. 
     
     
       10. The method of  claim 1 , further comprising introducing an amount of a high salt buffer into the capillary channel before injecting the amount of first fluid into the capillary channel. 
     
     
       11. The method of  claim 1 , further comprising introducing an amount of high salt buffer fluid into the capillary channel after injecting the amount of first fluid into the capillary channel. 
     
     
       12. The method of  claim 1 , further comprising introducing an amount of air into the capillary channel before injecting the amount of first fluid into the capillary channel. 
     
     
       13. The method of  claim 1 , further comprising introducing an amount of air into the capillary channel after injecting the amount of first fluid into the capillary channel. 
     
     
       14. The method of  claim 1 , further comprising introducing an amount of immiscible fluid into the capillary channel before injecting the amount of first fluid into the capillary channel. 
     
     
       15. The method of  claim 1 , further comprising introducing an amount of immiscible fluid into the capillary channel after injecting the amount of first fluid into the capillary channel. 
     
     
       16. The method of  claim 1 , wherein the first fluid comprises a first test compound. 
     
     
       17. The method of  claim 1 , further comprising repeating steps (a)-(d) with a plurality of separate fluid sources, each of the separate fluid sources comprising a different test compound. 
     
     
       18. The method of  claim 1 , wherein the plurality of different fluid sources comprises at least 1000 separate fluid sources, each separate fluid source comprising a different test compound. 
     
     
       19. The method of  claim 18 , wherein at least one of the at least 1000 separate sources comprises an inactivating compound. 
     
     
       20. The method of  claim 1 , wherein the first fluid comprises a nonaqueous fluid. 
     
     
       21. The method of  claim 20 , wherein the nonaqueous fluid comprises DMSO, DMF, acetone or an alcohol. 
     
     
       22. The method of  claim 20 , wherein the amount of first fluid injected into the capillary channel is less than 1 μl. 
     
     
       23. The method of  claim 20 , wherein the amount of first fluid injected into the capillary channel is less than 100 nl. 
     
     
       24. The method of  claim 20 , wherein the amount of first fluid injected into the capillary channel is less than 10 nl. 
     
     
       25. The method of  claim 20 , wherein the amount of first fluid injected into the capillary channel is less than 1 nl. 
     
     
       26. The method of  claim 20 , wherein the amount of first fluid injected into the capillary channel is between about 0.1 pl and 100 nl. 
     
     
       27. The method of  claim 20 , wherein the capillary channel has a cross sectional area of between about 10 μm 2  and 1×10 5  m 2 , and the first selected time is less than 30 seconds. 
     
     
       28. The method of  claim 27 , wherein the first selected time is less than about 10 seconds. 
     
     
       29. The method of  claim 27 , wherein the first selected time is less than about 5 seconds. 
     
     
       30. The method of  claim 27 , wherein the first selected time is less than or equal to about 1 second. 
     
     
       31. The method of  claim 1 , wherein the capillary channel is in fluid communication with at least a first microscale channel disposed in a body structure, and the first fluid is transported through the capillary channel and into the first microscale channel. 
     
     
       32. The method of  claim 31 , wherein the first microscale channel is intersected by and in fluid communication with at least a second microscale channel disposed in the body structure. 
     
     
       33. The method of  claim 32 , further comprising: 
       flowing a component of a biochemical system into the first microscale channel from the second microscale channel whereby the first fluid contacts the component of the biochemical system; and  
       detecting an effect of the first fluid on the component of the biochemical system.  
     
     
       34. The method of  claim 1 , further comprising introducing first and second high salt fluid regions into the capillary channel before and after, respectively, the amount of first fluid injected into the capillary channel. 
     
     
       35. The method of  claim 34 , further comprising introducing first and second low salt fluid regions into the capillary channel before the first high salt fluid region and after the second high salt fluid region, respectively. 
     
     
       36. A method of reducing or eliminating spontaneous injection, the method comprising: 
       (i) dipping an open end of an open ended fluid-filled capillary element into a source of a first fluid and applying a negative pressure to the first fluid, thus injecting the first fluid into the capillary element; and, (ii) changing the negative pressure to a positive pressure or a zero pressure, thereby reducing or eliminating spontaneous injection of the first fluid.  
     
     
       37. The method of  claim 36 , the method further comprising: 
       (iii) dipping the open end of the open ended fluid filled capillary element into a source of a second fluid;  
       (iv) changing the positive pressure or zero pressure to a negative pressure, thereby injecting the second fluid into the capillary element.  
     
     
       38. The method of  claim 36 , comprising applying a negative pressure of about −1 to about −2 psi. 
     
     
       39. The method of  claim 36 , comprising changing the negative pressure to a positive pressure of about 1 to about 3 psi. 
     
     
       40. The method of  claim 39 , comprising changing the negative pressure to a positive pressure of about 0.1 to about 0.3 psi. 
     
     
       41. The method of  claim 36 , comprising changing the negative pressure to a pressure substantially equal to the magnitude of the spontaneous injection. 
     
     
       42. The method of  claim 36 , comprising applying a negative pressure in one or more wells and changing the negative pressure in the one or more wells to a positive pressure or a zero pressure concurrent with step (ii). 
     
     
       43. The method of  claim 42 , wherein the wells comprise one or more of: a substrate well, an enzyme well, and a waste well. 
     
     
       44. A method of screening one or more samples in a microfluidic enzyme inhibition assay, the method comprising: 
       (i) introducing one or more samples into a microfluidic device; and,  
       (ii) introducing at least one inactivating reagent before the one or more samples, after the one or more samples, or between at least two of the one or more samples.  
     
     
       45. The method of  claim 44 , wherein the inactivating reagent inhibits substantially 100% of an enzyme activity. 
     
     
       46. The method of  claim 44 , further comprising determining a percent inhibition for one or more samples by comparing a level of inhibition for the one or more samples to a 100% inhibition level of the inactivating reagent. 
     
     
       47. The method of  claim 44 , further comprising introducing the inactivating reagent after about every 10, about every 25, about every 50, or about every 100, samples. 
     
     
       48. The method of  claim 44 , further comprising applying an electric field through the microfluidic device to transport the one or more samples and the inactivating reagent through the device. 
     
     
       49. The method of  claim 44 , further comprising applying pressure through the microfluidic device to transport the one or more samples and the inactivating reagent through the device. 
     
     
       50. A microfluidic device, comprising: 
       a glass or quartz body structure having disposed therein an integrated channel structure than includes at least first and second intersecting microscale channels, at least the first channel terminating in a substantially rectangular opening in the body structure;  
       a capillary element having a capillary channel disposed therethrough, and at least one end of the capillary element that is substantially rectangular, the substantially rectangular end of the capillary element being inserted into the substantially rectangular opening in the body structure and positioned such that the capillary channel in the capillary element is in fluid communication with at least first microscale channel in the body structure.  
     
     
       51. The microfluidic device of  claim 50 , wherein the body structure comprises: 
       a first planar substrate having a first surface having a plurality of intersecting grooves fabricated thereon, and at least a first substantially rectangular notch fabricated into the surface along one edge of the substrate, at least one of the plurality of grooves terminating in the first notch;  
       a second planar substrate comprising a first surface having a second substantially rectangular notch fabricated in the first surface of the second substrate along an edge of the second substrate, the first surface of the second planar substrate overlaying the first surface of the first planar substrate whereby the second notch and the first notch form the substantially rectangular opening in the body structure.  
     
     
       52. The method of  claim 51  wherein the capillary element is substantially coplanar with the first and second planar substrates. 
     
     
       53. The microfluidic device of  claim 51 , wherein the capillary channel in the capillary element comprises a cross-sectional area that is approximately equal to a cross sectional area of the at least first microscale channel in the body structure. 
     
     
       54. The microfluidic device of  claim 51 , wherein the capillary element comprises a curved portion that is not coplanar with the first and second planar substrates. 
     
     
       55. The microfluidic device of  claim 51 , wherein the capillary element comprises a sheath disposed over an outer surface of the capillary element. 
     
     
       56. The microfluidic device of  claim 51 , wherein the sheath is selected from plastic, polyimide and polytetrafluoroethylene. 
     
     
       57. The microfluidic device of  claim 51 , wherein the capillary element is fixedly inserted into the opening. 
     
     
       58. A method of joining a capillary element to a microfluidic device having an integrated channel network disposed therein, comprising: 
       providing a glass or quartz microfluidic device having a body structure with at least first and second intersecting microscale channels disposed therein, and having a substantially rectangular opening disposed in the body structure, at least one of the first and second microscale channels terminating in and being in communication with the opening;  
       providing a substantially rectangular capillary element having first and second ends and a capillary channel disposed through the capillary element from the first end to the second end, and wherein the sec6nd end has a substantially rectangular shape; and  
       inserting the second end of the capillary element into the opening, the capillary channel in the capillary element being positioned to be in fluid communication with the at least one of the first and second microscale channels that is in communication with the opening.  
     
     
       59. A method of introducing a fluid material into a microfluidic device, comprising: 
       providing a microfluidic device, comprising:  
       a glass or quartz body structure having disposed therein an integrated channel network that includes at least first and second intersecting microscale channels, at least the first channel terminating in a substantially rectangular opening in the body structure. a capillary element having first and second ends and a capillary channel disposed therethrough from the first to the second end, the second end of the capillary element being substantially rectangular, the second end of the capillary element being inserted into the substantially rectangular opening in the body structure and positioned such that the capillary channel in the capillary element is in fluid communication with at least first microscale channel in the body structure;  
       pacing the first end of the capillary element into a source of the fluid material;  
       drawing an amount of the fluid material into the capillary channel;  
       transporting the amount of the fluid material through the capillary channel into the at least one of the first and second microscale channels.  
     
     
       60. The method of  claim 59 , wherein the drawing and transporting steps comprise applying an electric field between the first end of the capillary channel and integrated channel network in the body structure to move the first fluid into and through the capillary channel electrokinetically. 
     
     
       61. A microfluidic device comprising: 
       a glass or quartz body structure having at least first and second channel segments disposed therein, the first and second channel segments each having first and second ends, the first end of the first channel being in fluid communication with the first end of the second channel at a first fluid junction; and  
       a capillary element attached to and extending from the body structure, the capillary element comprising a capillary channel disposed therethrough, the capillary channel being in fluid communication at one end with the first and second channel segments at the first fluid junction.  
     
     
       62. The microfluidic device of  claim 61 , wherein the capillary channel meets and is in fluid communication with the first channel segment at an angle between 45° and 90°. 
     
     
       63. The method of  claim 62 , wherein the body structure comprises a plurality of intersecting channels arranged in a first plane, and wherein the capillary element extends out of the first plane at an angle between about 45° and 90°. 
     
     
       64. The microfluidic device of  claim 61 , wherein a portion of the first channel segment that is adjacent to and in fluid communication with the first fluid junction is collinear with a portion of the second channel segment that is adjacent to and in fluid communication with the first fluid junction. 
     
     
       65. The microfluidic device of  claim 61 , wherein the second channel segment comprises a first cross-sectional dimension substantially equivalent to a first cross-sectional dimension of the first channel segment and a second cross sectional dimension less than one half of a second cross sectional dimension of the first channel segment. 
     
     
       66. The microfluidic device of  claim 65 , wherein the second cross-sectional dimension of the second channel segment is no greater than one tenth the second cross sectional dimension of the first channel segment. 
     
     
       67. The microfluidic device of  claim 61 , wherein the second end of the second channel segment is in fluid communication with a fluid source of at least a first component of a biochemical system. 
     
     
       68. The microfluidic device of  claim 61 , wherein the second end of the first channel segment is in fluid communication with a waste reservoir. 
     
     
       69. The microfluidic device of  claim 61 , wherein the second ends of the first and second channel segments are in fluid communication with first and second reservoirs, respectively, the first and second reservoirs being disposed in the body structure. 
     
     
       70. The microfluidic device of  claim 61 , comprising at least first and second electrodes disposed in electrical contact with a fluid in the first and second reservoirs, respectively. 
     
     
       71. The microfluidic device of  claim 70 , wherein the at least first component of the biochemical system produces a detectable signal indicative of a relative level of functioning of the biochemical system. 
     
     
       72. The microfluidic device of  claim 61 , further comprising a material transport system for transporting a first material through the capillary channel into the first channel segment and for concomitantly directing a flow of a second material from the second channel segment through the first fluid junction into the first channel segment. 
     
     
       73. The microfluidic device of  claim 61 , wherein the body structure comprises: 
       a first substrate having at least a first planar surface, the first planar surface having first and second groove segments disposed thereon;  
       a second substrate having a first planar surface, the first planar surface of the second substrate being mated with the first planar surface of the first substrate, the first and second groove segments defining the first and second channel segments.  
     
     
       74. The microfluidic device of  claim 73 , wherein the capillary element is attached to the body structure and the capillary channel is in fluid communication with the first fluid junction via an opening disposed through the body structure. 
     
     
       75. The microfluidic device of  claim 74 , wherein the opening disposed through the body structure comprises an opening disposed through at least one of the first and second substrates, the capillary element being fixedly inserted into the opening. 
     
     
       76. The microfluidic device of  claim 74 , wherein the opening in the body structure comprises a third groove segment disposed in the first surface of the first substrate and having first and second ends, the first end of the third groove segment terminating at one end at a first edge of the first planar surface of the first substrate and defining a third channel segment having first and second ends in the body structure, the first end of the third channel segment defining an opening in a first edge of the body structure, and the second end of the third channel segment being in fluid communication with the first fluid junction. 
     
     
       77. The microfluidic device of  claim 76 , wherein the capillary element is attached to the body structure at the first edge of the body structure and wherein the capillary channel is in fluid communication with the third channel segment. 
     
     
       78. A method of transporting material in a microscale channel, comprising: 
       introducing a first fluid into the channel, having a first electroosmotic mobility, and a first conductivity;  
       introducing a second fluid into the channel, having a second electroosmotic mobility and a second conductivity different from the first conductivity; and  
       varying a voltage gradient applied across a length of the channel to maintain a substantially constant average electroosmotic flow rate, despite a change in a total resistance of the channel.  
     
     
       79. The method of  claim 78 , further comprising the step of monitoring the total resistance of the channel, and varying the voltage gradient based upon variations in the total resistance. 
     
     
       80. The method of  claim 79 , wherein the voltage gradient is varied as a function of the total resistance of the channel. 
     
     
       81. The method of  claim 78 , wherein the first fluid comprises a test compound. 
     
     
       82. The method of  claim 78 , wherein the first fluid comprises a high salt buffer. 
     
     
       83. The method of  claim 78 , wherein the second fluid comprises a low salt buffer. 
     
     
       84. The method of  claim 78 , further comprising a plurality of discrete volumes of the first fluid into the channel, each of the discrete volumes of first fluid being separated by at least a separate discrete volume of the second fluid. 
     
     
       85. The method of  claim 84 , wherein each of the plurality of discrete first fluid regions comprises a different test compound. 
     
     
       86. The method of  claim 78 , wherein the microscale channel is in fluid communication with a capillary channel that is disposed in a capillary element, the capillary channel having two ends, one end being in fluid communication with the microscale channel, and the other end being open and wherein the introducing steps comprise alternatively contacting the open end of the capillary channel with a source of first fluid and a source of second fluid, to introduce first fluid and second fluid, respectively, into the capillary channel and into the microscale channel. 
     
     
       87. The method of  claim 78 , further comprising detecting a reaction within the microscale channel. 
     
     
       88. A microfluidic system. comprising: 
       a microfluidic device comprising a microscale channel disposed therein, the microscale channel containing varying volumes of first and second fluids over time, the first and second fluids having first and second conductives, respectively;  
       an electrical controller operably coupled to the microscale channel for applying a variable electric field across a length of the microscale channel;  
       a computer operably coupled to the electrical controller, and appropriately programmed to instruct the controller to vary the electric field to maintain a constant average electroosmotic flow rate within the channel, despite a change in total resistance across the length of the channel resulting from the varying volumes of first and second fluids over time.  
     
     
       89. The microfluidic system of  claim 88 , wherein the microfluidic device comprises a capillary element having a capillary channel disposed therein, the capillary channel having a first open end and a second end in fluid communication with the microscale channel. 
     
     
       90. The microfluidic system of  claim 89 , further comprising a source of first fluid and a source of second fluid, the first fluid having a first conductivity and the second fluid having a second conductivity, each of the sources of first and second fluids being positioned to be alternatively in fluid communication with the capillary element. 
     
     
       91. The microfluidic system of  claim 88 , wherein the microfluidic device comprises at least a second microscale channel disposed therein, the second microscale channel intersecting the first microscale channel. 
     
     
       92. The microfluidic system of  claim 88 , wherein the microfluidic device comprises a plurality of reservoirs disposed therein, each of the reservoirs being in fluid communication with the first microscale channel. 
     
     
       93. The microfluidic system of  claim 88 , wherein the controller comprises a plurality of electrodes, each of the plurality of electrodes operably coupled to a different terminus of the microscale channel. 
     
     
       94. The microfluidic system of  claim 88 , wherein the controller measures a resistance across the length of the microscale channel. 
     
     
       95. The microfluidic system of  claim 88 , wherein the computer comprises appropriate programming to vary the electric field in response to the change in total resistance across the length of the microscale channel. 
     
     
       96. The microfluidic system of  claim 88 , further comprising a detector in sensory communication with the microscale channel for detecting a reaction within the microscale channel.